Field of the Invention
The present invention relates in general to methods, devices and systems for electromagnetic identification, and in particular, to electromagnetic identification labels and systems for anti-counterfeiting, authentication and tamper-protection.
Various techniques and methods have been used to prevent the counterfeiting of products and provide a means of authentication. Copy protection and authentication methods have included printing or stamping microscopic features that are difficult to reproduce, such as optical holograms (for example, U.S. Pat. No. 5,729,365). Other methods have employed the use of detectable chemical or biological compounds such as monoclonal antibodies. Yet other methods have made use of materials and inks that exhibit a detectable visual response when subject to a unique physical stimulus, such as fluorescent dye or thermochromic ink (for example, U.S. Pat. No. 6,264,107). An undesirable feature of the majority of these methods is that they either require line-of-sight or require the use of relatively expensive and complex scanner hardware.
Rather than marking the object or article directly, it is common practice to affix to the object a label containing the aforementioned physical properties for anti-counterfeiting and authentication. Examples of the use of labels for these purposes can be found in a wide range of items and products, including important documents, photographic film, audio/video tapes, designer jeans, expensive bottles of wine, designer athletic shoes, jewelry and other luxury items. Once again, the function of these labels generally rely on optical means of detection (for example, U.S. Pat. No. 4,558,318). The use of electromagnetic tags or markers for anti-counterfeiting, authentication and tamper-protection is ALSO known in the art. The basic elements of an electromagnetic tagging system are shown in FIG. 2. The radio-frequency id tag or label is affixed or embedded in an object. The object can then be scanned by a reader device that can ascertain the id code of the tag and compare it to a known value in a database (such as that shown in U.S. Pat. No. 6,201,474, for example). (An example of authentication might involve determining which of two luxury watches belongs to a given customer. An example of anti-counterfeiting might involve determining whether a particular example of a watch is genuine, or a copy.) A primary advantage of electromagnetic id labels is that line-of-sight is not required and the electronic scanner devices do not require complex electronic hardware.
The simplest form of electromagnetic tags to not provide any identification (ID) information, but simply provide a detectable signal commonly used in retail antitheft systems (U.S. Pat. No. 4,694,283, for example). Conventional electromagnetic id tags can be chip-based or “chipless”. As a general matter, the information contained in chip-based tags is encoded via digital modulation of the RF signal by the electronic chip (U.S. Pat. No. 5,347,263, for example), while the information contained in chipless tags is encoded in analog signals such as frequency resonance peaks which can then be translated into a binary code (e.g., U.S. Pat. No. 5,444,223). Implementations that combine both chip-based and chipless signals are also possible (see, e.g. U.S. Pat. No. 6,232,870).
For both chip-based and chipless electromagnetic tag labels, the signal or data produced by the label is pre-programmed and fixed, set either by the data in the chip or set by the physical geometry and mechanical properties of the tag elements. While these fixed-data tags have enabled some increase in security by assigning a unique serial number to the object, there exists a continuing need for more secure ways to mark and identify products, in a “strong” manner, for identification, authentication and anti-counterfeiting.